The borehole of a hydrocarbon producing well typically contains fluid comprising a liquid fraction. This liquid fraction may originate from one or more earth formations penetrated by the well borehole. Alternately, the liquid fraction may be drilling fluid or drilling “mud” used in the drilling operation to lubricate the drill bit, to remove drill cuttings from the well, and to control formation pressures that might be encountered in drilling. Liquid may also be added to the well borehole in production intervention operations.
Although sometimes beneficial, borehole liquid can be detrimental to hydrocarbon production. As an example, the borehole of a gas producing well may contain a liquid that has either been placed within the borehole operational purposes such as pressure control. Alternately, the gas well may also be producing a liquid fraction thereby creating a liquid loading situation within the borehole. Regardless of the origin, pressure exerted by borehole liquid can hinder or even terminate or “kill” the production of the desired gas phase.
Various techniques can be used to remove liquid from a well borehole. Perhaps the earliest technique involves “bailing” liquid from the borehole by sequentially lowering, retrieving, and dumping at the surface an open bailer container using a cable as a means for conveying the bailer container. The amount of liquid removed per sequence or “trip” of the bailer container is limited by the relatively small capacity of the container. Furthermore, bailing with an open bailer container provides no means for pressure control. If the well presents potential pressure problems, suitable surface pressure control equipment, such as blow out preventer, is required. Liquid removal using coiled tubing methodology allows well pressures to be controlled. The mobilization and deployment of coil tubing apparatus is, however, time consuming and costly. Time and cost are especially significant for offshore wells where a dedicated barge is required for a coiled tubing operation if there is insufficient deck space on a wellhead platform.